Subject phosphonate carbanions

Aldol addition and related reactions of enolates and enolate equivalents are the subject of the first part of Chapter 2. These reactions provide powerful methods for controlling the stereochemistry in reactions that form hydroxyl- and methyl-substituted structures, such as those found in many antibiotics. We will see how the choice of the nucleophile, the other reagents (such as Lewis acids), and adjustment of reaction conditions can be used to control stereochemistry. We discuss the role of open, cyclic, and chelated transition structures in determining stereochemistry, and will also see how chiral auxiliaries and chiral catalysts can control the enantiose-lectivity of these reactions. Intramolecular aldol reactions, including the Robinson annulation are discussed. Other reactions included in Chapter 2 include Mannich, carbon acylation, and olefination reactions. The reactivity of other carbon nucleophiles including phosphonium ylides, phosphonate carbanions, sulfone anions, sulfonium ylides, and sulfoxonium ylides are also considered. 

Indirect electrophilic amination is achievable when dialkyl phosphonate carbanions (Li counter ion) reacts with di- r/-butyl azodicarboxylate, and the a-hydrazino products (Scheme 43) are then subjected to catalytic hydrogenation which liberates the free amine ... 

Scheme 52 outlines a sequence of reaction steps of an unusual nature in which an alka-1,2-dienylphosphonic diester is subjected to initial lithiation followed by silylation at this stage the silylated carbanion 424 may be protonated to yield the [l-(trimethylsilyl)alk-2enyl]phosphonate (425). However, 424 also reacts with SO2 to yield the thienyl-2-phosphonic diester 427 the intermediate in this process has been identified as the sulphine 426 ... 

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